Annotation of src/usr.bin/ssh/canohost.c, Revision 1.7
1.1 deraadt 1: /*
1.7 ! deraadt 2: *
! 3: * canohost.c
! 4: *
! 5: * Author: Tatu Ylonen <ylo@cs.hut.fi>
! 6: *
! 7: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
! 8: * All rights reserved
! 9: *
! 10: * Created: Sun Jul 2 17:52:22 1995 ylo
! 11: *
! 12: * Functions for returning the canonical host name of the remote site.
! 13: *
! 14: */
1.1 deraadt 15:
16: #include "includes.h"
1.7 ! deraadt 17: RCSID("$Id: canohost.c,v 1.6 1999/11/23 22:25:53 markus Exp $");
1.1 deraadt 18:
19: #include "packet.h"
20: #include "xmalloc.h"
21: #include "ssh.h"
22:
1.6 markus 23: /* Return the canonical name of the host at the other end of the socket.
1.1 deraadt 24: The caller should free the returned string with xfree. */
25:
1.6 markus 26: char *
27: get_remote_hostname(int socket)
1.1 deraadt 28: {
1.6 markus 29: struct sockaddr_in from;
30: int fromlen, i;
31: struct hostent *hp;
32: char name[MAXHOSTNAMELEN];
33:
34: /* Get IP address of client. */
35: fromlen = sizeof(from);
36: memset(&from, 0, sizeof(from));
37: if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
38: debug("getpeername failed: %.100s", strerror(errno));
39: fatal_cleanup();
40: }
41: /* Map the IP address to a host name. */
42: hp = gethostbyaddr((char *) &from.sin_addr, sizeof(struct in_addr),
43: from.sin_family);
44: if (hp) {
45: /* Got host name, find canonic host name. */
46: if (strchr(hp->h_name, '.') != 0)
47: strlcpy(name, hp->h_name, sizeof(name));
48: else if (hp->h_aliases != 0
49: && hp->h_aliases[0] != 0
50: && strchr(hp->h_aliases[0], '.') != 0)
51: strlcpy(name, hp->h_aliases[0], sizeof(name));
52: else
53: strlcpy(name, hp->h_name, sizeof(name));
54:
55: /* Convert it to all lowercase (which is expected by the
56: rest of this software). */
57: for (i = 0; name[i]; i++)
58: if (isupper(name[i]))
59: name[i] = tolower(name[i]);
60:
61: /* Map it back to an IP address and check that the given
62: address actually is an address of this host. This is
63: necessary because anyone with access to a name server
64: can define arbitrary names for an IP address. Mapping
65: from name to IP address can be trusted better (but can
66: still be fooled if the intruder has access to the name
67: server of the domain). */
68: hp = gethostbyname(name);
69: if (!hp) {
70: log("reverse mapping checking gethostbyname for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name);
71: strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
72: goto check_ip_options;
73: }
74: /* Look for the address from the list of addresses. */
75: for (i = 0; hp->h_addr_list[i]; i++)
76: if (memcmp(hp->h_addr_list[i], &from.sin_addr, sizeof(from.sin_addr))
77: == 0)
78: break;
79: /* If we reached the end of the list, the address was not
80: there. */
81: if (!hp->h_addr_list[i]) {
82: /* Address not found for the host name. */
83: log("Address %.100s maps to %.600s, but this does not map back to the address - POSSIBLE BREAKIN ATTEMPT!",
84: inet_ntoa(from.sin_addr), name);
85: strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
86: goto check_ip_options;
87: }
88: /* Address was found for the host name. We accept the host name. */
89: } else {
90: /* Host name not found. Use ascii representation of the address. */
91: strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
92: log("Could not reverse map address %.100s.", name);
93: }
94:
95: check_ip_options:
96:
97: /* If IP options are supported, make sure there are none (log and
98: disconnect them if any are found). Basically we are worried
99: about source routing; it can be used to pretend you are
100: somebody (ip-address) you are not. That itself may be "almost
101: acceptable" under certain circumstances, but rhosts
102: autentication is useless if source routing is accepted. Notice
103: also that if we just dropped source routing here, the other
104: side could use IP spoofing to do rest of the interaction and
105: could still bypass security. So we exit here if we detect any
106: IP options. */
1.1 deraadt 107: {
1.6 markus 108: unsigned char options[200], *ucp;
109: char text[1024], *cp;
110: int option_size, ipproto;
111: struct protoent *ip;
112:
113: if ((ip = getprotobyname("ip")) != NULL)
114: ipproto = ip->p_proto;
115: else
116: ipproto = IPPROTO_IP;
117: option_size = sizeof(options);
118: if (getsockopt(0, ipproto, IP_OPTIONS, (char *) options,
119: &option_size) >= 0 && option_size != 0) {
120: cp = text;
121: /* Note: "text" buffer must be at least 3x as big as options. */
122: for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
123: sprintf(cp, " %2.2x", *ucp);
124: log("Connection from %.100s with IP options:%.800s",
125: inet_ntoa(from.sin_addr), text);
126: packet_disconnect("Connection from %.100s with IP options:%.800s",
127: inet_ntoa(from.sin_addr), text);
128: }
129: }
1.1 deraadt 130:
1.6 markus 131: return xstrdup(name);
1.1 deraadt 132: }
133:
134: static char *canonical_host_name = NULL;
135: static char *canonical_host_ip = NULL;
136:
137: /* Return the canonical name of the host in the other side of the current
1.6 markus 138: connection. The host name is cached, so it is efficient to call this
1.1 deraadt 139: several times. */
140:
1.6 markus 141: const char *
142: get_canonical_hostname()
1.1 deraadt 143: {
1.6 markus 144: /* Check if we have previously retrieved this same name. */
145: if (canonical_host_name != NULL)
146: return canonical_host_name;
147:
148: /* Get the real hostname if socket; otherwise return UNKNOWN. */
149: if (packet_get_connection_in() == packet_get_connection_out())
150: canonical_host_name = get_remote_hostname(packet_get_connection_in());
151: else
152: canonical_host_name = xstrdup("UNKNOWN");
1.1 deraadt 153:
1.6 markus 154: return canonical_host_name;
1.1 deraadt 155: }
156:
157: /* Returns the IP-address of the remote host as a string. The returned
158: string need not be freed. */
159:
1.6 markus 160: const char *
161: get_remote_ipaddr()
1.1 deraadt 162: {
1.6 markus 163: struct sockaddr_in from;
164: int fromlen, socket;
1.1 deraadt 165:
1.6 markus 166: /* Check if we have previously retrieved this same name. */
167: if (canonical_host_ip != NULL)
168: return canonical_host_ip;
169:
170: /* If not a socket, return UNKNOWN. */
171: if (packet_get_connection_in() != packet_get_connection_out()) {
172: canonical_host_ip = xstrdup("UNKNOWN");
173: return canonical_host_ip;
174: }
175: /* Get client socket. */
176: socket = packet_get_connection_in();
1.1 deraadt 177:
1.6 markus 178: /* Get IP address of client. */
179: fromlen = sizeof(from);
180: memset(&from, 0, sizeof(from));
181: if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
182: debug("getpeername failed: %.100s", strerror(errno));
183: fatal_cleanup();
184: }
185: /* Get the IP address in ascii. */
186: canonical_host_ip = xstrdup(inet_ntoa(from.sin_addr));
1.1 deraadt 187:
1.6 markus 188: /* Return ip address string. */
189: return canonical_host_ip;
1.1 deraadt 190: }
191:
192: /* Returns the port of the peer of the socket. */
193:
1.6 markus 194: int
195: get_peer_port(int sock)
1.1 deraadt 196: {
1.6 markus 197: struct sockaddr_in from;
198: int fromlen;
1.1 deraadt 199:
1.6 markus 200: /* Get IP address of client. */
201: fromlen = sizeof(from);
202: memset(&from, 0, sizeof(from));
203: if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
204: debug("getpeername failed: %.100s", strerror(errno));
205: fatal_cleanup();
206: }
207: /* Return port number. */
208: return ntohs(from.sin_port);
1.1 deraadt 209: }
210:
211: /* Returns the port number of the remote host. */
212:
1.6 markus 213: int
214: get_remote_port()
1.1 deraadt 215: {
1.6 markus 216: int socket;
1.1 deraadt 217:
1.6 markus 218: /* If the connection is not a socket, return 65535. This is
219: intentionally chosen to be an unprivileged port number. */
220: if (packet_get_connection_in() != packet_get_connection_out())
221: return 65535;
1.1 deraadt 222:
1.6 markus 223: /* Get client socket. */
224: socket = packet_get_connection_in();
1.1 deraadt 225:
1.6 markus 226: /* Get and return the peer port number. */
227: return get_peer_port(socket);
1.1 deraadt 228: }
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